64 bit assignment trouble on a 32 bit platform

[kum]

hi,

UINT64 a64; // UINT64 has been typedefed as long long unsigned int
UINT32 a32, b32;
a32 = x; // some value
b32 = y; // some value

a64 = a32 * b32;
a64 += a32 + b32;

Is it necessary to type-cast both a32 and b32 to make above statements
to work as expected? Without casting, I find that addition works while
the multiplication does not. Is there a compiler option to make this
work without casting? I am using gcc 4.1.1 on an xscale platform.

Thanks,
kumaresh